Dometic 310 vs 320: Key Differences Every RV Owner Must Know

You’ll pick the Dometic 310 when space and simplicity matter. It’s a compact, round 10″ rough‑in toilet with a pressure‑enhanced swirl.

It features a lower depth and lighter build, making it ideal for tight RV or marine heads.

Choose the 320 for an elongated, sturdier ceramic bowl, rimless multi‑spout wash, and larger 11″ valve.

It also has heavier components that boost cleaning and durability.

Both models use foot‑pedal gravity flushes; keep water pressure between 40–60 PSI for best results.

More specifics follow if you want them.

Dometic 320 vs 310 Toilets : Side-by-Side Comparison

Feature	Dometic 310	Dometic 320
Bowl Shape	Round – compact, space-saving	Elongated – residential comfort
Dimensions	~17″ H x 14″ W x 19″ D	~17″ H x 14.3″ W x 21–22″ D
Rough-In Requirement	~10″–11″	~11″–12″ (needs more clearance)
Flush System	Pressure-enhanced swirl, single-spout	Rim-wash swirl, multi-spout
Build & Material	Ceramic bowl + plastic base	Full vitreous ceramic, heavier
Water Use	~1 pint per flush (efficient)	Slightly higher, but better coverage
Comfort & Ergonomics	Space-saving, tighter fit	More comfortable, larger seat
Durability	Mid-tier, lighter components	Premium, heavier duty
Best For	Small RVs, vans, marine heads	Larger RVs, long-term stays

Key Takeaways

• 310 is compact round-bowl (≈17″ H x 14″ W x 19″ D) for tight RV/marine spaces; 320 is elongated and deeper (≈17″ H x 14.3″ W x 21–22″ D).
• 310 uses a pressure-enhanced single-spout swirl; 320 uses rim-wash rimless distribution for quieter, more thorough rinsing.
• 320 has a larger 11″ valve, heavier ceramic, and more robust components, offering greater durability than the 310.
• 310 fits tighter rough-ins (≈10″–11″); 320 needs ~2–3″ more front-to-back clearance and a slightly larger rough-in.

Design and Bowl Shape Comparison

While both the Dometic 310 and 320 share ceramic construction and smooth lines for easy cleaning, they diverge in bowl shape, footprint, and installation requirements, so you should choose based on space and comfort priorities.

You’ll find the 310 uses a tall, classic round bowl that reduces footprint and fits 10″ rough-in layouts, improving fit in compact RV bathrooms and aiding sit/stand ergonomics.

The 320 shifts to an elongated bowl and an 11″ rough-in, increasing seating area and comfort but demanding more floor length and possible plumbing or flooring modification for retrofit.

Both accept wood slow-close seats matched to bowl shape; color options like White or Bone influence aesthetics.

Pick the 310 for compact layout, the 320 for comfort where space allows.

AMSOIL’s superior cold-start performance and lower pour point cold crank viscosity can be a useful comparison point when considering material and performance trade-offs between products.

Flushing Mechanism and Operation

Compare performance by testing gravity flush power, foot-pedal actuation, and how water is distributed during the cycle. You’ll find both models use a gravity system with pedal operation, but the 320’s rim spray gives more even coverage than the 310’s single-spout flow. Kirkland synthetic oils offer cost-effective performance for routine maintenance that aligns with standard driving needs and intervals; consider cost per quart when budgeting for regular service.

Evaluate pedal feel, seal response, and post-flush bowl cleanliness to judge real-world effectiveness. The 320 also features an enameled elongated seat with residential height for added comfort.

Gravity Flush Performance

How does the gravity-based flush in the Dometic 310 and 320 actually work? You initiate a ball-valve release that lets stored water descend, using gravity to generate flow and clearing waste without pumps.

The 310 relies on a pressure-enhanced gravity swirl that channels water in a circular pattern for targeted rinsing. Its bowl combines ceramic top and plastic base, slightly reducing mass and stability. Timken hubs, known for their durability, are often recommended when long service life is a priority.

The 320 uses a rim-wash swirl, distributing water through multiple spouts around a fully vitreous ceramic bowl for more even coverage and quieter operation.

Both valves are foot-pedal actuated and need coordinated timing to optimize volume and flow.

The 320’s larger 11″ valve and heavier-duty components generally yield greater durability and marginally improved wash efficiency.

Additionally, proper installation and correct water pressure are important for optimal performance 40-60 PSI.

Foot Pedal Operation

Because the foot pedal directly controls the flush valve, you get hands-free, variable flushing that’s simple and reliable: pressing the pedal mechanically lifts the watertight flush ball to release stored water into the bowl, and releasing it immediately stops flow to prevent waste.

You control flush volume by how far you depress the pedal, enabling partial or full gravity-driven flushes to clear the bowl while conserving water.

The pedal is modular and interchangeable across Dometic 300/310/320/321 series, so you can replace or repair the unit independently with common parts from RV suppliers.

Expect durable, intuitive placement for ergonomic use in tight spaces.

Note valve wear is typical; isolate system pressure and drain low points before servicing to avoid overflow.

The Dometic 310 also offers a water-efficient flush that uses just one pint per flush.

Mechanical hydraulic designs like billet steel components are often favored for durability and minimal moving parts.

Rim Water Distribution

With the foot pedal controlling the valve lift, rim water distribution completes the flush cycle by channeling pressurized water through molded rim passages to rinse the bowl. You’ll see even distribution from integrated rim channels that generate pressurized flow, producing a high-speed swirling action that cleans the bowl quickly with minimal water.

The gravity-flush valve lifts when you depress the pedal, releasing water sealed by multiple O-rings. Releasing the pedal reseats the valve to stop flow and prevent drips. Vacuum breakers and sealing grommets prevent backflow and leaks at the rim-to-bowl interface.

Both 310 and 320 use vitreous ceramic rims to resist staining and preserve channel efficiency. Serviceable valve kits let you replace seals or valves to restore pressurized rim performance. Regular inspection can prevent leaks and flow issues by catching debris or worn seals early inspect valve.

Periodic cleaning and protective treatments can help maintain surface integrity and reduce buildup from environmental contaminants like tree sap.

Materials, Seat Features, and Build Quality

Although they look similar at a glance, the Dometic 310 and 320 differ in material application and ergonomics: both use durable plastic bowls and seats, brass-and-plastic components in the flush ball/shaft kits, and metal pedal assemblies under two-piece plastic covers, but the 320’s deeper, elongated bowl and slightly thicker molding improve structural strength and seating comfort while the 310’s rounder, shallower profile saves space.

You’ll find corrosion-resistant brass shafts, plastic composite lids, and pedal covers sized for repeated use. Seats secure tightly for travel. Maintenance is simplified by gravity-only internals and common replacement kits. Quick reference:

Component	310	320
Bowl shape	Round	Elongated
Material thickness	Thinner	Thicker
Ergonomics	Space-saving	More comfortable

The 320 is also noticeably larger and heavier, making it better suited for larger RVs.

Size, Installation Requirements, and Fit

Now you’ll compare footprint and dimensions to see which model fits your bathroom layout: the 310’s compact, round bowl suits tighter spaces while the 320’s elongated, deeper bowl needs more floor length.

Check mounting and plumbing alignment next—both use standard RV gravity-flush outlets and similar hardware, but the 320 may shift drain alignment and require minor cabinetry or flooring adjustments.

Finally, verify clearance and accessibility around pedal, front space, and mounting height to guarantee comfortable use and proper seal/flange compatibility.

Consider also the long-term maintenance benefits of choosing a model that offers better lubricity and protection for fleet or high-use applications, as additives and treatments can extend component life.

Footprint and Dimensions

Because the 310 uses a round bowl while the 320 uses an elongated one, you’ll need about 2–3 inches more front-to-back clearance for the 320 even though their heights and widths are nearly the same.

The 310 measures roughly 17″ H x 14″ W x 19″ D; the 320 runs about 16.6–17″ H x 14.3″ W x 21–22″ D.

Use the 310 in tight van or marine heads where depth is under 20″; choose the 320 for cabins or larger RV bathrooms when ergonomics matter. Regular maintenance like periodic flushing and inspection helps keep RV plumbing odor- and bacteria-free, especially after installation of a new toilet annual sanitization.

Rough-in bolt spacing stays standard (≈12″–14″), so floor cutout changes are minimal, but verify door swing and adjacent cabinetry for the 320’s extra length before ordering or installing.

Additionally, many popular marine and RV brands offer compact models in this size range, so check compatibility with your unit as several options are available.

Mounting and Plumbing

When you install a Dometic 310 or 320, plan for a secure floor-flange mount and correct plumbing clearances to guarantee leak-free operation and proper pedal function.

You’ll use the toilet’s bolt pattern with at least four screws—eight is preferable—using supplied T‑bolts, washers and nuts tightened to 30–40 in·lb, alternating sides to avoid base distortion.

Confirm the outlet drain fully seats into the flange; use a nitrile floor seal and clean the flange before fitting.

The pedal needs a flat, stable surface so the seal can compress evenly.

Water supply fittings and a vacuum breaker are included to meet RV/travel‑trailer standards; verify pipe compatibility and that the bowl length won’t interfere with nearby fixtures.

Measure from the mounting bolts to the back wall to confirm rough‑in compatibility with the model rough‑in distance.

Also ensure your water connections use food-grade materials to maintain safe potable water supply.

1. Verify flange condition and alignment
2. Torque mounting nuts alternately
3. Confirm drain and seal engagement

Clearance and Accessibility

Start by measuring the footprint and rough‑in to confirm which model fits your space: the 310’s 20″ depth and 10″ rough‑in suit tighter RV baths, while the 320’s 22″ depth and 11″ rough‑in need roughly 1″ more clearance behind the bowl and about 3″ more front clearance overall.

You’ll prefer the 310 when wall-to-bolt distance is constrained; its 20″ length and two-bolt pattern ease retrofit into older rigs.

Choose the 320 when you can accommodate its elongated ceramic bowl and slightly taller profile for residential comfort.

Both share an 18″ seat height and low-profile base for simpler floor alignment and sealing.

Verify a 3″ discharge flange match, confirm pedal clearance, and plan modifications if rough-in falls short. The 320 also offers a gravity flush system that is activated by a foot pedal for operation.

Performance, Cleaning and Reliability

Although both toilets deliver reliable flushing, the 320 targets a cleaner, more thorough rinse with a rimless bowl and full-rim water distribution. The 320’s wider distribution improves bowl coverage.

The 310 favors a compact footprint and conventional single-spout flush that simplifies installation and maintenance. You’ll find both install straightforward; the 310 often drops into older mounts with minimal modification. Ensure you perform compatibility and preparation checks before installation to avoid surprises during setup and to confirm proper fit with your vehicle’s bed and components installation compatibility.

Cleaning-wise, rimless 320 reduces hidden crevices, making it easier to sanitize. The 310’s china-on-plastic layout needs more attention at edges.

Inspect seals and valves periodically on either unit to prevent leaks. Additionally, for many van and RV owners a compressor fridge is the most energy-efficient option, typically drawing about 24 Ah/day in small popular models.

1. Performance: 320 = broader water coverage; 310 = space-efficient, reliable flush.
2. Cleaning: rimless 320 easier to sanitize; 310 needs edge-focused cleaning.
3. Reliability: seals/valves are wear points; install quality dictates longevity.

Which Model Suits Your RV Lifestyle?

Price and features will guide your buy, but your daily RV routine determines which toilet fits best. You’ll choose the 310 if space and simplicity matter: tall, round ceramic bowl, compact footprint, single-spout gravity flush, easier fit in tight wet bays.

Pick the 320 if comfort and cleaning performance matter more: elongated residential-style bowl, rim-fed flush for full-coverage rinsing, improved seal design. Both use ceramic, slow-close seats, and foot-pedal gravity operation, so maintenance and durability are similar. The price difference is small, so consider whether the additional features are worth it.

1. Short trips / tight bathrooms: 310 — space-efficient, simpler water distribution.
2. Long stays / home comfort: 320 — better seating, superior rim flush.
3. DIY maintenance: both — ceramic durability, check seals and valve compatibility.

Frequently Asked Questions

Are Replacement Parts Widely Available for Each Model?

Yes — replacement parts are widely available for both models. You’ll find common components (flush ball seals, gasket kits, floor/base seals, ball-and-shaft kits) across major RV suppliers and online retailers.

The 310 is very common so parts are abundant; the 320 shares many compatible parts with the 300 series, though some installation-specific items (rough-in, mounting flanges, valve cables) may need model verification before purchase.

Can Either Model Be Converted to a Macerator System?

Want to retrofit a macerator to a gravity toilet? You probably can’t do it cleanly. You’ll face space, discharge-port and sealing challenges, and no official Dometic kit exists for either model.

Third‑party macerator kits might be adapted, but they need electrical work, hose/adapters and likely structural mods—especially on the larger 320.

Unless you’re prepared for custom plumbing and cost, buying a purpose‑built macerator toilet is the practical choice.

Do These Toilets Comply With Marine Sanitation Regulations?

Yes — they comply when installed per instructions. You’ll connect either model above a sealed holding tank (Type III MSD configuration), maintain required water flow/pressure, and follow manufacturer sealing, venting, and winterization guidance.

You won’t use them as direct-discharge or macerator units without approved conversion. Keep seals, hoses, and installation dimensions correct to prevent leaks and guarantee adherence with marine sanitation regulations and local discharge laws.

Are There Color or Finish Customization Options Beyond White and Bone?

No — you won’t find factory color or finish options beyond white and bone. Both models use glazed ceramic for durability and odor resistance.

The 310 has a plastic seat (natural white/bone) and the 320 is full vitreous ceramic (white/bone).

No official aftermarket paints or stains are supported, and altering finishes can void warranty or affect performance.

You can add nonpermanent accessories like seat covers, but permanent color changes aren’t offered.

What Warranties and Customer Support Services Are Offered?

Think of warranty fine print as a polite robot promising to fix things: you get a standard manufacturer warranty covering defects and material failures, with terms varying by purchase source (Dometic.com, dealer, preinstalled, Delibox).

You’ll have support for registration, claims, troubleshooting, parts, and installation guidance; rough-in mismatches can affect coverage. Keep proof of purchase and registration handy, avoid non‑approved mods, and contact Dometic or dealers for specifics and claim processing.

Making the Upgrade: Should You Pick Space or Comfort?

Choosing between the Dometic 310 and 320 comes down to fit and function.

The 320 offers a more modern bowl and stronger flush. It also provides a splash-free clearing experience and slightly better materials.

The 310 is compact and reliable, making it ideal for tight spaces. It features proven simplicity and durability.

You’ll want the 320 if you prioritize powerful flushing and modern design.

Pick the 310 if you need a space-saving, dependable option.

Either way, you’re getting RV-grade durability—these toilets are practically indestructible.

Match dimensions and plumbing to ensure the best long-term value and performance.

Last update on 2025-09-08 / Affiliate links / Images from Amazon Product Advertising API